Electrical properties and chemical sensing application of gallium trioxide and gallium nitride nanowires

One-dimensional nano-structured materials have been researched intensively due to unique characteristics. Single crystalline nanowires (NWs) have large surface to volume ratio and high thermal/chemical stability which are desirable properties for chemical sensing application. In this thesis, NWs of Ga2O3 and GaN are researched for nano-sensor application. At first, NWs were synthesized by vapor-liquid-solid growth mechanism while morphology and properties of NWs were controlled by experimental variables such as catalyst, growth temperature, and carrier gas. Transferring these NWs to the substrates, three types of device structure (Bush, random multiple and single NWs devices) were made with Pt contacts. Ga2O3 multiple NWs grown in C reduction showed high response time and conduction mechanism which is similar to thin film device even though grain boundaries did not exist. On the other hand, Ga2O3 multiple NWs grown in N2 showed inverse signal behavior possibly resulting from surface reaction between oxide and hydrogen. Sensing result of Ga2O 3 bush NWs device was similar to previous studies of Ga2O 3 multi-grain ceramic structures. Sensitivity of Ga2O 3 bush NWs had improved compared to Ga2O3 multiple NWs devices. GaN multiple NWs and single NWs also showed fast response and low noise levels, although sensitivity was not comparable to Ga2O 3 devices. Electrical conductance of GaN NWs devices was orders of magnitude higher than that of to Ga2O3 NWs devices, which can help the signal process of sensor. In conclusion, we have demonstrated NWs sensors for hydrogen detection working at low temperature and with rapid response.